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We performed ab initio valence-space in-medium similarity renormalization group calculations based on chiral nucleon-nucleon and three-nucleon interactions to study the neutron-rich nuclei around N=28, where the experimental and theoretical evidence point to a rapid transition from spherical to rotational regimes. First, the rotational spectra of 40Mg, 42Si, and 44S are established theoretically, anchored by the calculated E2 transition strength. The results suggest that 40Mg and 42Si exhibit large deformations. After that, the erosion of the N=28 shell closure, especially the evolutions of shape deformation and the emergence of shape coexistence, are discussed in N=28 even-even isotones ranging from 40Mg to 48Ca. Finally, the shell evolution of N=28 in Mg and Si chains is discussed based on the experimental and predicted excitation energies of low-lying states. The results from our ab initio calculations align well with available experimental data, furnishing essential insights into the structure of neutron-rich nuclei, particularly deformations in the vicinity of 40Mg and 42Si.

New magic numbers have been discovered in the neutron-rich region of the nuclear chart. However, there has been a lack of research on proton-rich nuclei. 22O, the mirror nucleus of 22Si, is a double-magic nucleus bearing a high E(21+). Whether 22Si exhibits double-magic characters is an intriguing topic. To investigate this matter, we utilized ab initio valence space in-medium similarity renormalization group for 22Si/22O, and their nearby nuclei. Our ab initio calculations provide good descriptions for the double magicity of 22O, as well as the shell evolution of N=14 and Z=14 through E(21+). The computed E(21+) indicate that the closure of Z=14 sub-shell in proton-rich nuclei is weaker than the N=14 sub-shell closure in their mirror nuclei. Particularly, the calculated E(21+) of 22Si is 800 keV lower than the one of 22O. To further explore the magicity of 22Si, the mirror energy difference (MED) of 26Si/26Mg, 24Si/24Ne, as well as 22Si/22O are calculated. The results demonstrate that the calculated MEDs agree well with available experimental data, and the E(21+) values of 22,24,26Si are all lower than their respective mirror nuclei due to the Thomas-Ehrman shift with large s1/2 occupation. Moreover, our calculation provides that the many-body configurations of the low-lying state of 22Si/22O are nearly identical despite the fact that the states bearing large MED. In conclusion, our ab initio results suggest that 22Si is a double magic nucleus, similar to its mirror nucleus 22O, albeit with a lower E(21+).

We performed a quantitative study of the nuclei with proton numbers from Z=20 (Ca) to Z=28 (Ni) and neutron numbers ranging from N=38 to 52 using the realistic shell model, which merged the descriptions of nuclei around N=40 and N=50 within an extended model space. The 21+ excitation energy (E(21+)) is calculated for neutron-rich Cr, Fe, and Ni isotopes. The results suggest that the islands of inversion at N=40 and N=50 merge around the Cr chain, and the N=50 island of inversion is located below 78Ni. To demonstrate the prediction of the N=50 island of inversion, we calculated and compared the E(21+), B(E2;01+→21+), effective single-particle energies (ESPEs), the probability of particle-hole excitation, and the average occupations in the N=40 and N=50 isotones. Similar parabolic trends of E(21+) and B(E2;01+→21+) in the N=40 and 50 isotones are obtained. The calculated ESPEs give that the N=40 and N=50 shell gaps both increase with the variation of proton number from Z=20 (Ca) to Z=28 (Ni). However, our calculations indicate that different particle-hole excitations dominate in the ground states of the N=40 and N=50 islands of inversion, with 2p2h and 4p4h configurations being prominent in N=40 isotones, whereas 2p2h excitations are most important in the N=50 isotones. Furthermore, large occupations of the intruder quadrupole partner orbitals are also obtained in N=40 and N=50 isotones in our realistic shell model calculations.

Spectroscopic factors involving well bound nucleons in light nuclei are calculated with standard shell model, no-core shell model and Gamow shell model. Continuum coupling is included exactly in the Gamow shell model, due to the use of the Berggren basis, which contains bound, resonance and scattering states. Conversely, it is absent from standard and no-core shell models, where a basis of harmonic oscillator states is used. As the A−1 nuclei for which spectroscopic factors are calculated are either weakly bound or unbound, coupling to continuum is prominent, even though the A nuclei are well bound. It is then showed that Gamow shell model can properly reproduce experimental data and is a predictive tool for detailed nuclear structure at drip-line, contrary to standard and no-core shell model.

Owing to the storage and transportation problems of hydrogen fuel, exploring new methods of the real-time hydrogen production from ammonia becomes attractive. In this paper, non-thermal arc plasma (NTAP) combining with NiO/Al2O3 catalyst is developed to produce hydrogen from ammonia with high efficiency and large scale. The effects of ammonia gas flow rate and discharge power on the gas temperature, electron density, the hydrogen production rate, and energy efficiency were investigated. Experimental results show that the optical emission spectrum of NTAP working with pure ammonia medium was dominated by the atom spectrum of Hα, Hβ, and molecular spectrum of NH component. Under the optimum experimental condition of plasma discharge, the highest energy efficiency of hydrogen production reached 783.4 L/kW⋅h at NH3 gas flow rate of 30 SLM. When the catalyst was added, and heated by the NTAP simultaneously, the energy efficiency further increased to 1080.0 L/kW⋅h.

High-cycle fatigue tests of Pt–Al bond coated and bare single crystal superalloys were conducted at 700 °C and 800 °C, aiming at investigating the effect of bond coat on the high-cycle fatigue properties of a single crystal superalloy. The impact of bond coat was studied merely on the tensile and creep properties of this superalloy, but was not found on the high-cycle fatigue behavior of this alloy. The experimental results showed that the bond coat was found to be beneficial at 800 °C or under low stresses at 700 °C owing to the fact that cracks were retarded by the fine grains in the IDZ, the P-type rafted γ′ phases in the substrate or the coat/substrate interface, respectively. However, the bond coat was detrimental under high stresses at 700 °C owing to the rapid propagation of the early cracking and the brittle nature of bond coat. Moreover, EBSD results showed the all bond coat cracks mainly initiated at the surface of the coated specimens and started from grains with {123} slip system within bond coat. Fatigue tested samples at 800 °C showed a comparatively higher Schmid factor value than that at 700 °C. Following the fatigue test, TEM tests indicated that in the superalloy close to the bond coat, the dislocation networks formed due to the activity of various slip systems at 700 °C; under 450 MPa at 800 °C in this region, a special a0 superdislocation with two segments of compact core was observed in the rafted γ′ phases.

The decay of the 13/2+ isomeric state in 183Hg was observed for the first time following the α decay of the 13/2+ isomer in 187Pb produced in the 142Nd(50Cr, 2p3n) reaction. Using α−γ delayed coincidence measurements, the half-life of this isomer was measured to be 290(30) μs. This isomer is proposed to deexcite by an unobserved low-energy M2 transition to the known 9/2− member of a strongly prolate-deformed 7/2−[514] band, followed by a 105-keV M1 transition to the bandhead. A lower limit of B(M2) ≥ 0.018 W.u. was deduced for the unobserved transition. The presumed retardation is proposed to be due to the notable shape change between the initial, nearly spherical, and the final, strongly deformed, states. A similar scenario is also considered for the 13/2+ isomer in 181Hg, suggesting both are cases of shape isomers. The B(M2) systematics of neutron transitions across the nuclear chart is discussed.

We have applied the Gamow shell model to calculate nuclear observables of 26−31Ne isotopes pertaining to one-neutron halo structure, these nuclei being situated close to neutron drip-line. As both many-body correlations and continuum coupling are taken into account in that approach, halo structure can be analyzed properly. Our calculations provide good descriptions of 26−31Ne, where asymptotic behavior is crucial for that matter. One-body density, neutron root-mean-square radii of 26−31Ne, and one-neutron overlap functions of 29,31Ne have been calculated as well. Our results support the presence of a one-neutron p-wave halo in 31Ne, already pointed out experimentally. A similar situation also occurs in the ground state of 29Ne, which is mainly a p-wave valence neutron coupled to the inner 28Ne core. The 3/2+ excited state of 29Ne, which is dominated by a d-wave valence neutron, has also been considered. A larger radius and more extended wave function occur for the ground state of 29Ne when compared to its 3/2+ first excited state. The present results suggest that 29Ne is a good candidate for one-neutron p-wave halo in the medium-mass region.

Prompt and delayed γ-ray spectroscopy of the neutron-deficient, semi-magic isotope 187Pb has been performed using the recoil-decay and isomer-decay tagging techniques at the Argonne Gas-Filled Analyzer. A new 5.15(15)-μs isomeric state at only 308 keV above the spherical 3/2− ground state is identified and classified as a shape isomer. A strongly-coupled band is observed on top of the isomer, which is nearly identical to the one built on the prolate 7/2−[514] Nilsson state in the isotone 185Hg. Based on this similarity and on the result of the potential-energy surface calculations, the new isomer in 187Pb is proposed to originate from the same configuration. The retarded character of the 308-keV (7/2−)→3/2gs− transition with a deduced B(E2)=5.6(2)×10−4 W.u. can be well explained by the significant difference between the prolate parent and spherical daughter configurations, leading to the shape isomerism. The excitation energy of the isomer is surprisingly low, being roughly half of the excitation energies of the known 0+ intruder bandheads in the neighboring 186,188Pb isotopes. The combined results of the present work and the previous α-decay and laser spectroscopy studies present evidence for triple shape coexistence at low energy in the negative-parity configurations of 187Pb, which is well reproduced by the potential-energy surface calculations.

With both three-nucleon force and continuum coupling included, we have developed a self-consistent ab initio Gamow shell model within the Gamow Hartree-Fock (GHF) basis obtained by the realistic interaction itself. With the chiral two-nucleon N3LO and three-nucleon N2LO interactions, the Gamow shell model has been applied to the mirror systems of Z=8 neutron-rich isotopes and N=8 proton-rich isotones, giving good agreements with data in binding energies, dripline positions and excitation spectra. The GHF calculated that the 0d3/2, 1s1/2 and 1p3/2 orbitals are resonances. The resonance states and their interplay with nonresonant continua play a crucial role in the descriptions of nuclei around driplines. Excitation spectra and Thomas-Ehrman shifts observed can be better described when both three-nucleon force and continuum coupling are considered in calculations. The three-nucleon force and continuum coupling produce a combined effect on the Thomas-Ehrman shift, e.g., for the 1/2+ resonance level of 19Na. The calculations help the understandings of related nuclear astrophysical processes.

This study compares experimental observations on plasma surface interactions and heat loads induced by Ion Cyclotron Resonance Heating (ICRH) in WEST medium size tokamak. When powering ICRH, core contamination by metallic impurities systematically results in an increase of the power radiated, often hardening the achievement of long discharges in H-mode at high power. The radiofrequency (RF) sheaths are excited mainly at proximity of ICRF antennas, resulting in an increase of metallic impurity sources. In the presence of RF sheaths, we show that most of the power reaching the wall can become carried by ions. Therefore, both heat loads and material sputtering are the result of ion fluxes on the various plasma facing components, such that some analogy between both phenomena can be made. By combining infrared with spectroscopic measurements, we show experimental evidences from WEST of RF-induced heat fluxes and their correlation with local production of impurity.

To study the compatibility especially the corrosion characteristic of structural material stainless steel (SS) with liquid lithium (Li) is an important factor for the simultaneous application of liquid Li and SS as a blanket material or potential plasma facing material (PFM) in future fusion devices. The corrosion behaviors of 304SS exposed to liquid Li at 700 K for 1320 hr under high vacuum were investigated. After exposure to liquid Li, 304SS produces non-uniform corrosion which includes corrosion products and grain boundary corrosion. Compared with the corrosion behaviors at 600 K and 640 K, temperature plays an important role in the corrosion behaviors of 304SS in static liquid Li. The weight loss, corrosion depth and corrosion products of 304SS specimens increase with the corrosion temperature. In general, the compatibility between 304SS and static liquid Li is relatively good under the experimental conditions. And besides, it is unexpectedly found that the compatibility of copper with Li is not good.

Starting from chiral two-nucleon (2NF) and chiral three-nucleon (3NF) potentials, we present a detailed study of 17Ne, a Borromean system, with the Gamow shell model which can capture continuum effects. More precisely, we take advantage of the normal-ordering approach to include the 3NF and the Berggren representation to treat bound, resonant and continuum states on equal footing in a complex-momentum plane. In our framework, 3NF is essential to reproduce the Borromean structure of 17Ne, while the continuum is more crucial for the halo property of the nucleus. The two-proton halo structure is demonstrated by calculating the valence proton density and correlation density. The astrophysically interesting 3/2− excited state has its energy above the threshold of the proton emission, and therefore the two-proton decay should be expected from the state.

Liquid lithium (Li) can partly ameliorate lifetime and power-exhaust issues of plasma facing components (PFCs) by enabling a self-healing, self-replenishing surface with a reduced susceptibility to neutron damage in future fusion devices. To assess operational stability and heat-exhaust capability under tokamak exposure, two generations of continuously flowing liquid Li (FLiLi) limiters on the concept of a thin flowing Li film have been successfully designed and tested in high performance discharges in EAST. The design uses a circulating Li layer with a thickness of

Gamow shell model (GSM) is usually performed within the Woods-Saxon (WS) basis in which the WS parameters need to be determined by fitting experimental single-particle energies including their resonance widths. In the multi-shell case, such a fit is difficult due to the lack of experimental data of cross-shell single-particle energies and widths. In this paper, we develop an ab-initio GSM by introducing the Gamow Hartree-Fock (GHF) basis that is obtained using the same interaction as the one used in the construction of the shell-model Hamiltonian. GSM makes use of the complex-momentum Berggren representation, then including resonance and continuum components. Hence, GSM gives a good description of weakly bound and unbound nuclei. Starting from chiral effective field theory and employing many-body perturbation theory (MBPT) (called nondegenerate Qˆ-box folded-diagram renormalization) in the GHF basis, a multi-shell Hamiltonian (sd-pf shells in this work) can be constructed. The single-particle energies and their resonance widths can also been obtained using MBPT. We investigated 23−28O and 23−31F isotopes, for which multi-shell calculations are necessary. Calculations show that continuum effects and the inclusion of the pf shell are important elements to understand the structure of nuclei close to and beyond driplines. Keywords: Gamow shell model, Gamow Hartree-Fock, Chiral effective field theory, Many-body perturbation theory, Resonance, Continuum

Three-nucleon force and continuum play important roles in reproducing the properties of atomic nuclei around driplines. Therefore it is valuable to build up a theoretical framework where both effects can be taken into account to solve the nuclear Schrödinger equation. To this end, in this letter, we have expressed the chiral three-nucleon force within the continuum Berggren representation, so that bound, resonant and continuum states can be treated on an equal footing in the complex-momentum space. To reduce the model dimension and computational cost, the three-nucleon force is truncated at the normal-ordered two-body level and limited in the sd-shell model space, with the residual three-body term being neglected. We choose neutron-rich oxygen isotopes as the test ground because they have been well studied experimentally, with the neutron dripline determined. The calculations have been carried out within the Gamow shell model. The quality of our results in reproducing the properties of oxygen isotopes around the neutron dripline shows the relevance of the interplay between three-nucleon force and the coupling to continuum states. We also analyze the role played by the chiral three-nucleon force, by dissecting the contributions of the 2π exchange, 1π exchange and contact terms. Keywords: Three-nucleon forces, Continuum, Gamow shell model, Unstable nuclei, Binding energy, Spectra

High-Z impurities production is often observed during Ion Cyclotron Range of Frequencies (ICRF) waves’ injection, which are likely due to RF sheath formation on solid materials. Based on Extreme UV (EUV) spectrometry data, this study in EAST consists in extracting information on plasma-surface interactions during ICRH. Intensities of the different spectral lines normalized to line-integrated plasma density, exhibit different parametric dependencies over scans of ICRH and LH power and for different toroidal phasing between straps. Materials close and magnetically-connected to an active antenna tend to show better correlation with ICRF parameters – such as power and feeding scheme – than those which are far away or not connected. ICRF phasing did not have influence on impurity, probably due to the absence of feedback control. It is further shown that the plasma content in impurities from divertor region better correlates with the total injected power rather than with ICRF power. Keywords: ICRH, Impurity source, EUV spectrometer

In this paper, we demonstrate the possibility of generating a non-Abelian Carroll–Field–Jackiw (CFJ) term in the theory of a non-Abelian gauge field coupled to a spin-3/2 field in the presence of the constant axial vector field. Applying two regularization schemes, we prove that this term is finite and ambiguous, particularly vanishing within the 't Hooft-Veltman scheme.

Synthesis and accumulation of the recently identified prostaglandin F2α receptor regulatory protein (FPRP) was found to correlate closely with lipid droplet accumulation by 3T3-L1 preadipose cells. FPRP, a transmembrane glycoprotein, has been shown to regulate the binding of ligand to certain seven-transmembrane receptors. Anti-FPRP immunohistochemistry, Western blotting, and metabolic labeling/immunoprecipitation experiments demonstrated that FPRP was not detectable in undifferentiated 3T3-L1 cells. Interestingly, low levels of FPRP mRNA were detected in the undifferentiated 3T3-L1 cells. After induction of adipose differentiation, FPRP mRNA increased ∼3 fold whereas FPRP synthesis increased ∼50 fold. Differentiation induction with either dexamethasone/insulin/isobutylmethylxanthine or the thiazolidinedione derivative ADD 4743 were both effective at inducing FPRP accumulation and accumulation of lipid droplets. By co-immunohistochemical and lipid staining, greater than 99% of the cells accumulating lipid droplets possessed FPRP. FPRP mRNA and protein are also found in rat adipose tissue. Treatment of 3T3-L1 cells with an FPRP anti-sense oligonucleotide during differentiation decreased FPRP accumulation and resulted in a decrease in lipid droplets without altering the level of induction of a late marker of adipocyte differentiation, glycerol-3-phosphate dehydrogenase activity. Transient expression of an FPRP cDNA in undifferentiated 3T3-L1 cells was insufficient to induce lipid droplet accumulation.—Orlicky, D. J., J. G. Lieber, C. L. Morin, and R. M. Evans. Synthesis and accumulation of a receptor regulatory protein associated with lipid droplet accumulation in 3T3-L1 cells. J. Lipid Res. 1998. 39: 1152–1161.